polarity of power cord - gateway fpd1520

"William Sommerwerck" wrote in message
. ..
On the monitor it should be marked or say something
in the manual.

"The Lady from Philadelphia" forgot the obvious. Power sockets almost
always
have their polarity marked.



I've certainly seen plenty of them that didn't though.

On 3ÔÂ28ÈÕ, ÏÂÎç4ʱ45·Ö, zirath wrote:
We recently got a gateway fpd1520 (15" lcd flatscreen) monitor from
ebay. It didn't have a power cord. It says it's a 12v dc 2.5a but it
doesn't give the polarity. A person from gateway said he thought it
wouldn't hurt the monitor if it got plugged in backwards but I'd rather
not try it.

Would appreciate any help.



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zirath wrote:
We recently got a gateway fpd1520 (15" lcd flatscreen) monitor from
ebay. It didn't have a power cord. It says it's a 12v dc 2.5a but it
doesn't give the polarity. A person from gateway said he thought it
wouldn't hurt the monitor if it got plugged in backwards but I'd rather
not try it.

Would appreciate any help.

Thanks to everyone for your help.

In ,
Arfa Daily typed on Fri, 28 Mar 2008 16:07:57 GMT:
"BillW50" wrote in message
. com...
In ,
Arfa Daily typed on Fri, 28 Mar 2008 12:52:58 GMT:
[...]
As for a transistor radio that uses PNP transistors, I haven't seen
one that uses transistors at all for many years, let alone PNP ones,
so I think you might be struggling to fit that into my "modern"
category, also.

Well Arfa... they still use transistors (both NPN and PNP types) in
modern equipment. The reason you don't see them anymore is do to the
magic of minturization. But they are still there, just neatly
packaged into what is known today as the intergrated circuit (IC
chip).

And I though I was pedantic !! Yes, of course ICs contain
transistors, and yes, I would accept that some of them may be PNP
types, depending on block function within the IC, but I don't think,
with the best will in the world, that this is the level of transistor
existence that William was referring to with his "transistor radio
using PNP transistors" scenario. In any event, in the case of an IC
taking a single polarity rail, it is irrelevant whether the
transistors inside are NPN or PNP or FETs or whatever. PNP
transistors are just used 'upside down', as are discrete PNP
transistors when used in any piece of single polarity rail equipment.
The ground is still (typically for //modern// equipment) the "-" side
of the power supply / battery.
Anyway, this is getting out of hand. The OP aked a simple question,
and I gave a simple answer. This afternoon, I was in a friend's
computer repair shop. Bear in mind that he deals with monitors of all
types and makes on a daily basis. I asked him how he would go about
determining the polarity of such a monitor, and he said that he would
stick one side of his ohm meter on one of the D connector locking
screws, and the other on each pin of the DC connector. When he found
the pin that read short to the connector locking screw, it was his
contention that he would have identified the "-" side of the power
supply. So that's pretty much exactly what I said. He also frowned
and shook his head, and said that he couldn't remember how many years
it had been since he had seen a DC connector that had the pin as the
"-".
Which is also pretty much what I said ...

Arfa

That would be okay if it were a negative ground system. But like what
William Sommerwerck mentioned, we don't know that. The way I would do it
is to ohm the the power in. And the lower resistance would be the
correct polarity. Although you would need another meter to read the
polarity of the ohm meter. As they are not standardized on multimeters.
You could also use a diode (or LED) to learn of the polarity of the
meter as well.

--
Bill

"BillW50" wrote in message
. com...
In ,
Arfa Daily typed on Fri, 28 Mar 2008 16:07:57 GMT:
"BillW50" wrote in message
. com...
In ,
Arfa Daily typed on Fri, 28 Mar 2008 12:52:58 GMT:
[...]
As for a transistor radio that uses PNP transistors, I haven't seen
one that uses transistors at all for many years, let alone PNP ones,
so I think you might be struggling to fit that into my "modern"
category, also.

Well Arfa... they still use transistors (both NPN and PNP types) in
modern equipment. The reason you don't see them anymore is do to the
magic of minturization. But they are still there, just neatly
packaged into what is known today as the intergrated circuit (IC
chip).

And I though I was pedantic !! Yes, of course ICs contain
transistors, and yes, I would accept that some of them may be PNP
types, depending on block function within the IC, but I don't think,
with the best will in the world, that this is the level of transistor
existence that William was referring to with his "transistor radio
using PNP transistors" scenario. In any event, in the case of an IC
taking a single polarity rail, it is irrelevant whether the
transistors inside are NPN or PNP or FETs or whatever. PNP
transistors are just used 'upside down', as are discrete PNP
transistors when used in any piece of single polarity rail equipment.
The ground is still (typically for //modern// equipment) the "-" side
of the power supply / battery.
Anyway, this is getting out of hand. The OP aked a simple question,
and I gave a simple answer. This afternoon, I was in a friend's
computer repair shop. Bear in mind that he deals with monitors of all
types and makes on a daily basis. I asked him how he would go about
determining the polarity of such a monitor, and he said that he would
stick one side of his ohm meter on one of the D connector locking
screws, and the other on each pin of the DC connector. When he found
the pin that read short to the connector locking screw, it was his
contention that he would have identified the "-" side of the power
supply. So that's pretty much exactly what I said. He also frowned
and shook his head, and said that he couldn't remember how many years
it had been since he had seen a DC connector that had the pin as the
"-".
Which is also pretty much what I said ...

Arfa

That would be okay if it were a negative ground system. But like what
William Sommerwerck mentioned, we don't know that. The way I would do it
is to ohm the the power in. And the lower resistance would be the correct
polarity. Although you would need another meter to read the polarity of
the ohm meter. As they are not standardized on multimeters. You could also
use a diode (or LED) to learn of the polarity of the meter as well.

--
Bill

JHC !!! Do you not understand the word "modern" ? Do you not understand the
phrase "... deals with monitors of all types on a daily basis" ? I repair
this stuff all day every day for a living. I have done for over 35 years. I
cannot remember the last time I saw a piece of kit of any description, which
employed a positive ground. My friend, who owns a computer repair shop, and
has done for many years, cannot remember the last time - if ever - that he
saw a monitor with an external power supply, that was not negative ground
with the connector sleeve as the negative connection.

With so much interconnectivity between household items now, there has had to
be a degree of standardisation on this issue, and it has evolved through a
general concensus amongst manufacturers, that negative ground will be the
convention.

As for your method of determining polarity, it makes no sense at all, unless
you are assuming a series diode, which is quite unlikely in most modern kit,
as it represents a waste of power due to its forward voltage drop. It may
even have a shunt protection diode, in which case, your 'test' will ensure
that the polarity is determined INcorrectly. Even if the device did have a
series diode, depending on where the supply first goes, there is still no
guarantee that there will be any reading at all on a standard multimeter on
ohms. If there is not any diode - series or shunt - any reading of ohms
obtained across the input socket, is unlikely to reveal anything meaningful.
What is your experience in fault-finding, I wonder, to have caused you to
have formulated such a bizarre method, and believe that it would
uncategorically give you a correct result ?

Arfa

Arfa Daily wrote:

JHC !!! Do you not understand the word "modern" ? Do you not understand the
phrase "... deals with monitors of all types on a daily basis" ? I repair
this stuff all day every day for a living. I have done for over 35 years. I
cannot remember the last time I saw a piece of kit of any description, which
employed a positive ground. My friend, who owns a computer repair shop, and
has done for many years, cannot remember the last time - if ever - that he
saw a monitor with an external power supply, that was not negative ground
with the connector sleeve as the negative connection.

With so much interconnectivity between household items now, there has had to
be a degree of standardisation on this issue, and it has evolved through a
general concensus amongst manufacturers, that negative ground will be the
convention.

As for your method of determining polarity, it makes no sense at all, unless
you are assuming a series diode, which is quite unlikely in most modern kit,
as it represents a waste of power due to its forward voltage drop. It may
even have a shunt protection diode, in which case, your 'test' will ensure
that the polarity is determined INcorrectly. Even if the device did have a
series diode, depending on where the supply first goes, there is still no
guarantee that there will be any reading at all on a standard multimeter on
ohms. If there is not any diode - series or shunt - any reading of ohms
obtained across the input socket, is unlikely to reveal anything meaningful.
What is your experience in fault-finding, I wonder, to have caused you to
have formulated such a bizarre method, and believe that it would
uncategorically give you a correct result ?


I guess that no one bothered to check out the link I posted to a
replacement supply that not only shows it to be center positive, but it
tells you which coaxial power plug you need.


--
aioe.org is home to cowards and terrorists

Add this line to your news proxy nfilter.dat file
* drop Path:*aioe.org!not-for-mail to drop all aioe.org traffic.

http://improve-usenet.org/index.html

In ,
Arfa Daily typed on Sun, 30 Mar 2008 14:23:08 GMT:
"BillW50" wrote in message
. com...
In ,
Arfa Daily typed on Fri, 28 Mar 2008 16:07:57 GMT:
"BillW50" wrote in message
. com...
In ,
Arfa Daily typed on Fri, 28 Mar 2008 12:52:58 GMT:
[...]
As for a transistor radio that uses PNP transistors, I haven't
seen one that uses transistors at all for many years, let alone
PNP ones, so I think you might be struggling to fit that into my
"modern" category, also.

Well Arfa... they still use transistors (both NPN and PNP types) in
modern equipment. The reason you don't see them anymore is do to
the magic of minturization. But they are still there, just neatly
packaged into what is known today as the intergrated circuit (IC
chip).

And I though I was pedantic !! Yes, of course ICs contain
transistors, and yes, I would accept that some of them may be PNP
types, depending on block function within the IC, but I don't think,
with the best will in the world, that this is the level of
transistor existence that William was referring to with his
"transistor radio using PNP transistors" scenario. In any event, in
the case of an IC taking a single polarity rail, it is irrelevant
whether the transistors inside are NPN or PNP or FETs or whatever.
PNP transistors are just used 'upside down', as are discrete PNP
transistors when used in any piece of single polarity rail
equipment. The ground is still (typically for //modern// equipment)
the "-" side of the power supply / battery.
Anyway, this is getting out of hand. The OP aked a simple question,
and I gave a simple answer. This afternoon, I was in a friend's
computer repair shop. Bear in mind that he deals with monitors of
all types and makes on a daily basis. I asked him how he would go
about determining the polarity of such a monitor, and he said that
he would stick one side of his ohm meter on one of the D connector
locking screws, and the other on each pin of the DC connector. When
he found the pin that read short to the connector locking screw, it
was his contention that he would have identified the "-" side of
the power supply. So that's pretty much exactly what I said. He
also frowned and shook his head, and said that he couldn't remember
how many years it had been since he had seen a DC connector that
had the pin as the "-".
Which is also pretty much what I said ...

Arfa

That would be okay if it were a negative ground system. But like what
William Sommerwerck mentioned, we don't know that. The way I would
do it is to ohm the the power in. And the lower resistance would be
the correct polarity. Although you would need another meter to read
the polarity of the ohm meter. As they are not standardized on
multimeters. You could also use a diode (or LED) to learn of the
polarity of the meter as well. --
Bill

JHC !!! Do you not understand the word "modern" ? Do you not
understand the phrase "... deals with monitors of all types on a
daily basis" ? I repair this stuff all day every day for a living. I
have done for over 35 years. I cannot remember the last time I saw a
piece of kit of any description, which employed a positive ground. My
friend, who owns a computer repair shop, and has done for many years,
cannot remember the last time - if ever - that he saw a monitor with
an external power supply, that was not negative ground with the
connector sleeve as the negative connection.
With so much interconnectivity between household items now, there has
had to be a degree of standardisation on this issue, and it has
evolved through a general concensus amongst manufacturers, that
negative ground will be the convention.

As for your method of determining polarity, it makes no sense at all,
unless you are assuming a series diode, which is quite unlikely in
most modern kit, as it represents a waste of power due to its forward
voltage drop. It may even have a shunt protection diode, in which
case, your 'test' will ensure that the polarity is determined
INcorrectly. Even if the device did have a series diode, depending on
where the supply first goes, there is still no guarantee that there
will be any reading at all on a standard multimeter on ohms. If there
is not any diode - series or shunt - any reading of ohms obtained
across the input socket, is unlikely to reveal anything meaningful.
What is your experience in fault-finding, I wonder, to have caused
you to have formulated such a bizarre method, and believe that it
would uncategorically give you a correct result ?
Arfa

Actually being an electrical engineer for 35 years, I could careless how
long your friend has been repairing computers. And the reason why the
ohm meter works is because all of the curcuits are in parallel with the
supply. Thus you will get a lower reading when the polarity is correct.
And you will get a higher reading when it is not correct. Thus as all of
the circuits are reversed biased.

Whether or not all manufactures use negative ground or not, I have no
idea. Although in all of my experience, I have learned to never assume
anything. And I have seen many strange designs. One of them had an OP
amp's output connected directly to ground. I was confused about that one
until I chatted with the designer. Then it all made sense.

--
Bill

JHC !!! Do you not understand the word "modern" ? Do you not understand
the phrase "... deals with monitors of all types on a daily basis" ? I
repair this stuff all day every day for a living. I have done for over 35
years. I cannot remember the last time I saw a piece of kit of any
description, which employed a positive ground. My friend, who owns a
computer repair shop, and has done for many years, cannot remember the
last time - if ever - that he saw a monitor with an external power supply,
that was not negative ground with the connector sleeve as the negative
connection.

With so much interconnectivity between household items now, there has had
to be a degree of standardisation on this issue, and it has evolved
through a general concensus amongst manufacturers, that negative ground
will be the convention.

As for your method of determining polarity, it makes no sense at all,
unless you are assuming a series diode, which is quite unlikely in most
modern kit, as it represents a waste of power due to its forward voltage
drop. It may even have a shunt protection diode, in which case, your
'test' will ensure that the polarity is determined INcorrectly. Even if
the device did have a series diode, depending on where the supply first
goes, there is still no guarantee that there will be any reading at all on
a standard multimeter on ohms. If there is not any diode - series or
shunt - any reading of ohms obtained across the input socket, is unlikely
to reveal anything meaningful. What is your experience in fault-finding, I
wonder, to have caused you to have formulated such a bizarre method, and
believe that it would uncategorically give you a correct result ?

Arfa


I've been working on this stuff for years as well, not as long as you, but I
haven't been alive as long as you've been at it either. I've never seen a
positive ground either, it would make no sense to do it that way. It's just
standard that this stuff is negative ground, and that metal parts of the
chassis are grounded for shielding, I've never once seen a case where this
wasn't true so it's good enough for me. If one is still in doubt, pop the
cover off and check the polarity of the filter lytics.

"BillW50" wrote in message
. com...
In ,
Arfa Daily typed on Sun, 30 Mar 2008 14:23:08 GMT:
"BillW50" wrote in message
. com...
In ,
Arfa Daily typed on Fri, 28 Mar 2008 16:07:57 GMT:
"BillW50" wrote in message
. com...
In ,
Arfa Daily typed on Fri, 28 Mar 2008 12:52:58 GMT:
[...]
As for a transistor radio that uses PNP transistors, I haven't
seen one that uses transistors at all for many years, let alone
PNP ones, so I think you might be struggling to fit that into my
"modern" category, also.

Well Arfa... they still use transistors (both NPN and PNP types) in
modern equipment. The reason you don't see them anymore is do to
the magic of minturization. But they are still there, just neatly
packaged into what is known today as the intergrated circuit (IC
chip).

And I though I was pedantic !! Yes, of course ICs contain
transistors, and yes, I would accept that some of them may be PNP
types, depending on block function within the IC, but I don't think,
with the best will in the world, that this is the level of
transistor existence that William was referring to with his
"transistor radio using PNP transistors" scenario. In any event, in
the case of an IC taking a single polarity rail, it is irrelevant
whether the transistors inside are NPN or PNP or FETs or whatever.
PNP transistors are just used 'upside down', as are discrete PNP
transistors when used in any piece of single polarity rail
equipment. The ground is still (typically for //modern// equipment)
the "-" side of the power supply / battery.
Anyway, this is getting out of hand. The OP aked a simple question,
and I gave a simple answer. This afternoon, I was in a friend's
computer repair shop. Bear in mind that he deals with monitors of
all types and makes on a daily basis. I asked him how he would go
about determining the polarity of such a monitor, and he said that
he would stick one side of his ohm meter on one of the D connector
locking screws, and the other on each pin of the DC connector. When
he found the pin that read short to the connector locking screw, it
was his contention that he would have identified the "-" side of
the power supply. So that's pretty much exactly what I said. He
also frowned and shook his head, and said that he couldn't remember
how many years it had been since he had seen a DC connector that
had the pin as the "-".
Which is also pretty much what I said ...

Arfa

That would be okay if it were a negative ground system. But like what
William Sommerwerck mentioned, we don't know that. The way I would
do it is to ohm the the power in. And the lower resistance would be
the correct polarity. Although you would need another meter to read
the polarity of the ohm meter. As they are not standardized on
multimeters. You could also use a diode (or LED) to learn of the
polarity of the meter as well. --
Bill

JHC !!! Do you not understand the word "modern" ? Do you not
understand the phrase "... deals with monitors of all types on a
daily basis" ? I repair this stuff all day every day for a living. I
have done for over 35 years. I cannot remember the last time I saw a
piece of kit of any description, which employed a positive ground. My
friend, who owns a computer repair shop, and has done for many years,
cannot remember the last time - if ever - that he saw a monitor with
an external power supply, that was not negative ground with the
connector sleeve as the negative connection.
With so much interconnectivity between household items now, there has
had to be a degree of standardisation on this issue, and it has
evolved through a general concensus amongst manufacturers, that
negative ground will be the convention.

As for your method of determining polarity, it makes no sense at all,
unless you are assuming a series diode, which is quite unlikely in
most modern kit, as it represents a waste of power due to its forward
voltage drop. It may even have a shunt protection diode, in which
case, your 'test' will ensure that the polarity is determined
INcorrectly. Even if the device did have a series diode, depending on
where the supply first goes, there is still no guarantee that there
will be any reading at all on a standard multimeter on ohms. If there
is not any diode - series or shunt - any reading of ohms obtained
across the input socket, is unlikely to reveal anything meaningful.
What is your experience in fault-finding, I wonder, to have caused
you to have formulated such a bizarre method, and believe that it
would uncategorically give you a correct result ?
Arfa

Actually being an electrical engineer for 35 years, I could careless how
long your friend has been repairing computers. And the reason why the ohm
meter works is because all of the curcuits are in parallel with the
supply. Thus you will get a lower reading when the polarity is correct.
And you will get a higher reading when it is not correct. Thus as all of
the circuits are reversed biased.

That is unmitigated nonsense. If there is a shunt protection diode, it will
be FORWARD biased when the polarity is WRONG. Also, the fact that my friend
repairs this stuff all day, and as an electrical engineer, you clearly do
not, that makes him an expert, compared to you ...


Whether or not all manufactures use negative ground or not, I have no
idea.

Well, as I repair this stuff all day as well, I *do* have an idea, so that
clearly also makes me more of an expert on this particular subject, than
you ...

Although in all of my experience, I have learned to never assume anything.
And I have seen many strange designs. One of them had an OP amp's output
connected directly to ground. I was confused about that one until I chatted
with the designer. Then it all made sense.

--
Bill

In general, I would agree with you not to assume anything, but some things
are a matter of convention, and in recent years, based on my direct
experience of such things, I would stick my neck on the line, and say that
this is one, and that all modern kit, manufactured for the domestic market,
employs circuitry with a negative ground, to which (most) external metalwork
is firmly bonded.

Arfa

Arfa Daily wrote:

snip

JHC !!! Do you not understand the word "modern" ? Do you not understand the
phrase "... deals with monitors of all types on a daily basis" ? I repair
this stuff all day every day for a living. I have done for over 35 years. I
cannot remember the last time I saw a piece of kit of any description, which
employed a positive ground. My friend, who owns a computer repair shop, and
has done for many years, cannot remember the last time - if ever - that he
saw a monitor with an external power supply, that was not negative ground
with the connector sleeve as the negative connection.

With so much interconnectivity between household items now, there has had to
be a degree of standardisation on this issue, and it has evolved through a
general concensus amongst manufacturers, that negative ground will be the
convention.

snip

I have resisted commenting but can do no longer; I don't know about the U.K.,
but I frequently encounter negative center coaxial power equipment in my
work. These are not monitors, but a variety of consumer and industrial
portable devices. When the connector is not labeled and I don't have docs,
I will physically inspect the internal wiring or the pcb that hosts the power
connector and also do resistance measurements between ground planes and the
power connector contacts to determine ground. The assumption that ground
planes are negative is a given in most instances. As for the subjective
label "modern", that is a religious issue that shouldn't be a factor in
good electronics practice

Michael